Semiconductor device and method of manufacturing the same

ABSTRACT

Disclosed are semiconductor devices and methods of manufacturing the same. The semiconductor device comprises a first transistor on a substrate, and a second transistor on the substrate. Each of the first and second transistors includes a plurality of semiconductor patterns vertically stacked on the substrate and vertically spaced apart from each other, and a gate dielectric pattern and a work function pattern filling a space between the semiconductor patterns. The work function pattern of the first transistor includes a first work function metal layer, the work function pattern of the second transistor includes the first work function metal layer and a second work function metal layer, the first work function metal layer of each of the first and second transistors has a work function greater than that of the second work function metal layer, and the first transistor has a threshold voltage less than that of the second transistor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. nonprovisional patent application claims priority under 35U.S.C § 119 of Korean Patent Application No. 10-2017-0079888 filed onJun. 23, 2017, the entire contents of which are hereby incorporated byreference.

BACKGROUND

Inventive concepts relate to semiconductor, and more particularly, to asemiconductor device including a gate-all-around type transistor and amethod of manufacturing the same.

A semiconductor device is considered to be an important factor inelectronic industry because of small size, multi-functionality, and/orlow fabrication cost. A semiconductor device may be categorized as anyone of a semiconductor memory device storing data and/or machinereadable instructions, a semiconductor logic device processingoperations of logic data, and a hybrid semiconductor device having bothmemory and logic elements. Semiconductor devices have been increasinglydesired, or alternatively required, for high integration with theadvanced development of the electronic industry. For example, asemiconductor device has been increasingly requested for highreliability, high speed, and/or multi-functionality. Semiconductordevices have gradually complicated and integrated to meet theserequested characteristics.

SUMMARY

Some embodiments of inventive concepts provide a semiconductor deviceincluding gate-all-around type transistors with various thresholdvoltages.

Some embodiments of inventive concepts provide a method of manufacturinga semiconductor device including gate-all-around type transistors withvarious threshold voltages.

According to some example embodiments of inventive concepts, asemiconductor device may comprise a first transistor on a substrate, anda second transistor on the substrate. Each of the first and secondtransistors includes a plurality of semiconductor patterns verticallystacked on the substrate and vertically spaced apart from each other,and a gate dielectric pattern and a work function pattern filling aspace between the semiconductor patterns. The work function pattern ofthe first transistor includes a first work function metal layer, thework function pattern of the second transistor includes the first workfunction metal layer and a second work function metal layer, the firstwork function metal layer of each of the first and second transistorshas a work function greater than that of the second work function metallayer, and the first transistor has a threshold voltage less than thatof the second transistor.

According to some example embodiments of inventive concepts, asemiconductor device may comprise a first transistor on a substrate anda second transistor on the substrate. Each of the first and secondtransistors includes a plurality of semiconductor patterns verticallystacked on the substrate and vertically spaced apart from each other,and a gate dielectric pattern and a work function pattern that fill aspace between the semiconductor patterns. The space of the firsttransistor has the same size as that of the space of the secondtransistor, the work function pattern of the first transistor comprisesa first work function metal layer, the work function pattern of thesecond transistor comprises a first work function metal layer and asecond work function metal layer, and the first transistor has athreshold voltage different from that of the second transistor.

According to some example embodiments of inventive concepts, a method ofmanufacturing a semiconductor device may comprise forming sacrificiallayers and semiconductor layers alternately and repeatedly stacked on asubstrate, forming sacrificial gate patterns crossing over thesacrificial layers and the semiconductor layers and extending in onedirection, removing the sacrificial gate patterns to form a first trenchand a second trench that expose the semiconductor layers and thesacrificial layers, selectively removing the sacrificial layers exposedto the first and second trenches, forming a first work function patternthat fills a first space between the semiconductor layers in the firsttrench, and forming a second work function pattern that fills a secondspace between the semiconductor layers in the second trench. The firstwork function pattern comprises a first work function metal layer, thesecond work function pattern comprises a first work function metal layerand a second work function metal layer, the first space and the secondspace have the same size as each other, and the first work functionpattern and the second work function pattern have different workfunctions from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plan view showing a semiconductor device accordingto some example embodiments of inventive concepts.

FIG. 2A illustrates a cross-sectional view taken along line A-A′ of FIG.1.

FIG. 2B illustrates a cross-sectional view taken along line B-B′ of FIG.1.

FIG. 2C illustrates a cross-sectional view taken along lines C-C′, D-D′,and E-E′ of FIG. 1.

FIG. 2D illustrates a cross-sectional view taken along lines F-F′, G-G′,and H-H′ of FIG. 1.

FIGS. 3, 5, 7, and 9 illustrate plan views showing a method ofmanufacturing a semiconductor device according to some exampleembodiments of inventive concepts.

FIGS. 4A, 6A, 8A, and 10A illustrate cross-sectional views taken alongline A-A′ of FIGS. 3, 5, 7, and 9, respectively.

FIGS. 4B, 6B, 8B, and 10B illustrate cross-sectional views taken alongline B-B′ of FIGS. 3, 5, 7, and 9, respectively.

FIG. 10C illustrates a cross-sectional view taken along line C-C′ ofFIG. 9.

FIG. 10D illustrates a cross-sectional view taken along line D-D′ ofFIG. 9.

FIGS. 11 to 14 illustrate cross-sectional views showing a method offorming first to third gate electrodes according to some exampleembodiments of inventive concepts.

FIG. 15 illustrates an enlarged cross-sectional view of section M ofFIG. 2B, partially showing a sixth transistor of a semiconductor deviceaccording to some example embodiments of inventive concepts.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates a plan view showing a semiconductor device accordingto some example embodiments of inventive concepts. FIG. 2A illustrates across-sectional view taken along line A-A′ of FIG. 1. FIG. 2Billustrates a cross-sectional view taken along line B-B′ of FIG. 1. FIG.2C illustrates a cross-sectional view taken along lines C-C′, D-D′, andE-E′ of FIG. 1. FIG. 2D illustrates a cross-sectional view taken alonglines F-F′, G-G′, and H-H′ of FIG. 1.

Referring to FIGS. 1 and 2A to 2D, a substrate 100 may be provided toinclude first to sixth regions RG1 to RG6. The substrate 100 may be orinclude a semiconductor substrate. For example, the substrate 100 may bea silicon substrate or a germanium substrate. Alternatively, thesubstrate 100 may be or include a Silicon-On-Insulator (SOI) substrate.First to sixth transistors TR1 to TR6 may be respectively provided onthe first to sixth regions RG1 to RG6 of the substrate 100.

At least some of the first to sixth regions RG1 to RG6 of the substrate100 may be or include a memory cell region where a plurality of memorycells are formed to store data. For example, the memory cell region ofthe substrate 100 may be provided thereon with memory cell transistorsincluded in a plurality of SRAM cells. The first to sixth transistorsTR1 to TR6 may be some of the memory cell transistors.

Alternatively or additionally, at least some of the first to sixthregions RG1 to RG6 of the substrate 100 may be or include a logic cellregion where logic transistors are to be included in a logic circuit ofa semiconductor device. For example, logic transistors may be on thelogic cell region of the substrate 100. The first to sixth transistorsTR1 to TR6 may be some of the logic transistors. Inventive concepts,however, are not limited thereto.

The first to third transistors TR1 to TR3 on the first to third regionsRG1 to RG3 may have conductive types different from those of the fourthto sixth transistors TR4 to TR6 on the fourth to sixth regions RG4 toRG6. For example, the first to third transistors TR1 to TR3 on the firstto third regions RG1 to RG3 may be PMOSFETs, and the fourth to sixthtransistors TR4 to TR6 on the fourth to sixth regions RG4 to RG6 may beNMOSFETs.

A device isolation layer ST may be provided on the substrate 100. Thedevice isolation layer ST may define first and second upper patterns UP1and UP2 on an upper portion of the substrate 100. The first upperpattern UP1 may be on the first to third regions RG1 to RG3, and thesecond upper pattern UP2 may be on the fourth to sixth regions RG4 toRG6. The device isolation layer ST may fill trenches on opposite sidesof each of the first and second upper patterns UP1 and UP2. The deviceisolation layer ST may have a top surface lower than those of the firstand second upper patterns UP1 and UP2.

A first active pattern AP1 may be provided on the first upper patternUP1, and a second active pattern AP2 may be provided on the second upperpattern UP2. For example, the first active pattern AP1 may verticallyoverlap the first upper pattern UP1, and the second active pattern AP2may vertically overlap the second upper pattern UP2. The first andsecond active patterns AP1 and AP2 may have a linear shape extending ina second direction D2.

The first active pattern AP1 may include first channel patterns CH1 andfirst source/drain patterns SD1. Each of the first channel patterns CH1may be between a pair of the first source/drain patterns SD1. The secondactive pattern AP2 may include second channel patterns CH2 and secondsource/drain patterns SD2. Each of the second channel patterns CH2 maybe between a pair of the second source/drain patterns SD2.

The first channel pattern CH1 may include a plurality of firstsemiconductor patterns NS1 that are vertically stacked. The firstsemiconductor patterns NS1 may be spaced apart from each other in athird direction D3 perpendicular to a top surface of the substrate 100.The first semiconductor patterns NS1 may vertically overlap each other.Each of the first source/drain patterns SD1 may be in contact, e.g.direct contact, with sidewalls of the first semiconductor patterns NS1.For example, the first semiconductor patterns NS1 may connect a pair ofneighboring first source/drain patterns SD1 to each other. The firstchannel pattern CH1 may include three first semiconductor patterns NS1,but the number of the first semiconductor patterns NS1 is not especiallylimited to three, and may be more, or less, than three.

The second channel pattern CH2 may include a plurality of secondsemiconductor patterns NS2 that are vertically stacked. The secondsemiconductor patterns NS2 may be spaced apart from each other in thethird direction D3. The second semiconductor patterns NS2 may verticallyoverlap each other. Each of the second source/drain patterns SD2 may bein contact, e.g. direct contact, with sidewalls of the secondsemiconductor patterns NS2. The second channel pattern CH2 may includethree second semiconductor patterns NS2, but the number of the secondsemiconductor patterns NS2 is not especially limited to three, and maybe more, or less, than three.

The first semiconductor patterns NS1 at the same level may be formedfrom the same semiconductor layer. The first semiconductor patterns NS1at the same level may have the same, or substantially the same,thickness as each other. The first semiconductor patterns NS1 at thesame level may have the same, or substantially the same, semiconductormaterial as each other. The second semiconductor patterns NS2 at thesame level may be formed from the same semiconductor layer. The secondsemiconductor patterns NS2 at the same level may have the same, orsubstantially the same, thickness as each other. The secondsemiconductor patterns NS2 at the same level may have the same, orsubstantially the same, semiconductor material as each other. Forexample, the first and second semiconductor patterns NS1 and NS2 mayinclude one or more of silicon (Si), silicon germanium (SiGe), andgermanium (Ge).

The first semiconductor patterns NS1 at different levels may have thesame thickness as each other or different thicknesses from each other.The second semiconductor patterns NS2 at different levels may have thesame thickness as each other or different thicknesses from each other.

The first source/drain patterns SD1 may be or include epitaxial patternsformed from the first semiconductor patterns NS1 and the first upperpattern UP1 serving as a seed layer. The second source/drain patternsSD2 may be or include epitaxial patterns formed from the secondsemiconductor patterns NS2 and the second upper pattern UP2 serving as aseed layer. The first source/drain patterns SD1 and the secondsource/drain patterns SD2 may be formed with a chemical vapor deposition(CVD) process; however, inventive concepts are not limited thereto.

When the first to third transistors TR1 to TR3 are PMOSFETs, the firstsource/drain patterns SD1 may include a material that providescompressive strain to the first channel pattern CH1. For example, thefirst source/drain patterns SD1 may include a semiconductor element(e.g., SiGe) whose lattice constant is greater than that of asemiconductor element of the substrate 100. The first source/drainpatterns SD1 may be doped with P-type conductive impurities, forexample, boron (B).

When the fourth to sixth transistors TR4 to TR6 are NMOSFETs, the secondsource/drain patterns SD2 may include a material that provides tensilestrain to the second channel pattern CH2. For example, the secondsource/drain patterns SD2 may include a semiconductor element whoselattice constant is less than that of the semiconductor element of thesubstrate 100. Accordingly a mobility of carriers, e.g. electronmobility, may increase in a channel during operation of the transistor.Alternatively, the second source/drain patterns SD2 may include the samesemiconductor element as that of the substrate 100. The secondsource/drain patterns SD2 may be doped with N-type conductiveimpurities, for example, phosphorus (P) and/or arsenic (As).

First to sixth gate electrodes GE1 to GE6 may be provided to extend in afirst direction D1, while running across the first and second channelpatterns CH1 and CH2. The first to sixth gate electrodes GE1 to GE6 mayrespectively cross over the first to sixth regions RG1 to RG6. The firstto sixth gate electrodes GE1 to GE6 may respectively include first tosixth work function patterns WF1 to WF6. The first to sixth gateelectrodes GE1 to GE6 may respectively further include first to sixthelectrode patterns EL1 to EL6. The first to sixth electrode patterns EL1to EL6 may be respectively on the first to sixth work function patternsWF1 to WF6. The first to sixth electrode patterns EL1 to EL6 may eachhave resistance, e.g. a sheet resistance, less than that of each of thefirst to sixth work function patterns WF1 to WF6. For example, the firstto sixth electrode patterns EL1 to EL6 may include one or more lowresistance or low resistivity metals such as aluminum (Al), tungsten(W), titanium (Ti), and tantalum (Ta).

The first to third work function patterns WF1 to WF3 of the first tothird gate electrodes GE1 to GE3 may respectively fill first to thirdspaces SP1 to SP3 each between the first semiconductor patterns NS1. Thefirst to third spaces SP1 to SP3 may be positioned between the firstsemiconductor patterns NS1 on the first to third regions RG1 to RG3,respectively. The fourth to sixth work function patterns WF4 to WF6 ofthe fourth to sixth gate electrodes GE4 to GE6 may respectively fillfourth to sixth spaces SP4 to SP6 each between the second semiconductorpatterns NS2. The fourth to sixth spaces SP4 to SP6 may be positionedbetween the second semiconductor patterns NS2 on the fourth to sixthregions RG4 to RG6, respectively.

The first to sixth spaces SP1 to SP6 at the same level may have thesame, or substantially the same, size as each other. For example, thefirst to sixth spaces SP1 to SP6 at the same level may have the samelength in the third direction D3.

The first to sixth work function patterns WF1 to WF6 of the first tosixth gate electrodes GE1 to GE6 may surround the first and secondsemiconductor patterns NS1 and NS2 (see FIG. 2C). For example, the firstto sixth work function patterns WF1 to WF6 may surround top surfaces,bottom surfaces, and sidewalls of the first and second semiconductorpatterns NS1 and NS2. In this sense, each of the first to sixthtransistors TR1 to TR6 may be a gate-all-around field effect transistor.

The first to third electrode patterns EL1 to EL3 of the first to thirdgate electrodes GE1 to GE3 may not respectively fill the first to thirdspaces SP1 to SP3. The first to third electrode patterns EL1 to EL3 maybe spaced apart from the first semiconductor patterns NS1 across thefirst to third work function patterns WF1 to WF3. The fourth to sixthelectrode patterns EL4 to EL6 of the fourth to sixth gate electrodes GE4to GE6 may not respectively fill the fourth to sixth spaces SP4 to SP6.The fourth to sixth electrode patterns EL4 to EL6 may be spaced apartfrom the second semiconductor patterns NS2 across the fourth to sixthwork function patterns WF4 to WF6.

A pair of gate spacers GS may be on opposite sidewalls of each of thefirst to sixth gate electrodes GE1 to GE6. The gate spacers GS mayextend in the first direction D1 along the first to sixth gateelectrodes GE1 to GE6. The gate spacers GS may have top surfaces higherthan those of the first to sixth gate electrodes GE1 to GE6. The firstto sixth work function patterns WF1 to WF6 on the first and secondchannel patterns CH1 and CH2 may extend in the third direction D3 alonginner walls of the gate spacers GS. For example, the gate spacers GS mayinclude one or more of SiCN, SiCON, and SiN. Alternatively, the gatespacers GS may include a multi-layer consisting of two or more of SiCN,SiCON, and SiN.

Gate capping layers CP may be on the first to sixth gate electrodes GE1to GE6. The gate capping layers CP may extend in the first direction D1along the first to sixth gate electrodes GE1 to GE6. The gate cappinglayers CP may have top surfaces coplanar with those of the gate spacersGS. The gate capping layers CP may include a material having an etchselectivity to a first interlayer dielectric layer 110, which will bediscussed below. For example, the gate capping layers CP may include oneor more of SiON, SiCN, SiCON, and SiN.

Barrier insulation patterns BP may be between the first and secondsource/drain patterns SD1 and SD2 and the first to sixth gate electrodesGE1 to GE6. The barrier insulation patterns BP may be either between thefirst semiconductor patterns NS1 vertically spaced apart from each otheror between the second semiconductor patterns NS2 vertically spaced apartfrom each other. The barrier insulation patterns BP may electricallyinsulate the first to sixth gate electrodes GE1 to GE6 from the firstand second source/drain patterns SD1 and SD2. The first to third spacesSP1 to SP3 may be defined by a pair of barrier insulation patterns BPhorizontally adjacent to each other and a pair of the firstsemiconductor patterns NS1 vertically adjacent to each other, and thefourth to sixth spaces SP4 to SP6 may be defined by a pair of thebarrier insulation patterns BP horizontally adjacent to each other and apair of the second semiconductor patterns NS2 vertically adjacent toeach other. The barrier insulation patterns BP may include, for example,a silicon nitride layer.

An interface layer IL may be provided to surround each of the first andsecond semiconductor patterns NS1 and NS2. The interface layers IL maycover, e.g. directly cover, the first and second semiconductor patternsNS1 and NS2. The interface layers IL may include, for example, a siliconoxide layer.

Gate dielectric layers GI may be between the first and secondsemiconductor patterns NS1 and NS2 and the first to sixth gateelectrodes GE1 to GE6. Each of the gate dielectric layers GI mayconformally fill a portion of a corresponding one of the first to sixthspaces SP1 to SP6. The gate dielectric layers GI may include a high-kdielectric material whose dielectric constant is greater than that of asilicon oxide layer. For example, the high-k dielectric material mayinclude one or more of hafnium oxide, hafnium silicon oxide, lanthanumoxide, zirconium oxide, zirconium silicon oxide, tantalum oxide,titanium oxide, barium strontium titanium oxide, barium titanium oxide,strontium titanium oxide, lithium oxide, aluminum oxide, lead scandiumtantalum oxide, and lead zinc niobate.

When the first to third transistors TR1 to TR3 are PMOSFETs, the secondtransistor TR2 may have a threshold voltage greater than, e.g. greaterin absolute value than, that of the first transistor TR1, and the thirdtransistor TR3 may have a threshold voltage greater than, e.g. greaterin absolute value than, that of the second transistor TR2.

The first work function pattern WF1 of the first transistor TR1 mayinclude a first work function metal layer W1. The second work functionpattern WF2 of the second transistor TR2 may include a same, orsubstantially, same first work function metal layer W1. In someembodiments, the material included in the first work function patternWF1 may be the same, or substantially the same, as that included in thesecond work function pattern WF2. The first work function metal layer W1may be or may include a metal nitride layer having a relatively highwork function. For example, the first work function metal layer W1 maybe a titanium nitride (TiN) layer or a titanium oxynitride (TiON) layer.

A work function control liner CL may be between the second work functionpattern WF2 and the first semiconductor patterns NS1. The work functioncontrol liner CL may generate a dipole, and thus a threshold voltage ofthe second transistor TR may be increased due to variation in energyband caused by the dipole. The work function control liner CL mayinclude a high-k dielectric material whose dielectric constant isgreater than that of a silicon oxide layer. For example, the workfunction control liner CL may include metal oxide such as lanthanumoxide or aluminum oxide.

Even though the first and second work function patterns WF1 and WF2 haveonly the same first work function metal layer W1, the work functioncontrol liner CL may cause the second transistor TR2 to have a thresholdvoltage greater than, e.g. greater in absolute value than, that of thefirst transistor TR1.

The third work function pattern WF3 of the third transistor TR3 mayinclude a first work function metal layer W1, a second work functionmetal layer W2, and other first work function metal layer W1sequentially stacked on the first semiconductor pattern NS1. In thethird space S3, the second work function metal layer W2 may have athickness greater than that of each of the first work function metallayers W1. The second work function metal layer W2 may be a metalnitride layer whose work function is less than that of the first workfunction metal layer W1. For example, the second work function metallayer W2 may be a silicon-doped titanium nitride (TiSiN) layer, asilicon-doped tantalum nitride (TaSiN) layer, an aluminum-doped titaniumnitride (TiAlN) layer, or an aluminum-doped tantalum nitride (TaAlN)layer.

The work function of the second work function metal layer W2 may bealtered by controlling a concentration of dopants such as silicon and/oraluminum. In this sense, the third work function pattern WF3 may becontrolled in work function by adjustment of an impurity concentrationin the second work function metal layer W2. For example, the second workfunction metal layer W2 may have an impurity concentration (e.g., asilicon and/or aluminum concentration) in a range from about 10 at % toabout 30 at %.

The first to third spaces SP1 to SP3 filled with the first to third workfunction patterns WF1 to WF3 may have the same, or substantially thesame, size as each other. Accordingly, the first to third work functionpatterns WF1 to WF3 filled between the first semiconductor patterns NS1may have the same, or substantially the same, thickness (e.g., a lengthin the third direction D3 of the first to third work function patternsWF1 to WF3). In some embodiments, the work function control liner CL maybe employed to cause the first to third work function patterns WF1 toWF3 to have different work functions from each other. Alternatively oradditionally, a combination of a plurality of work function metal layersmay be employed to cause the first to third work function patterns WF1to WF3 to have different work functions from each other. In certainembodiments, the second work function metal layer W2 may be controlledin doping concentration to cause the first to third work functionpatterns WF1 to WF3 to have different work functions from each other.

When the fourth to sixth transistors TR4 to TR6 are NMOSFETs, the fifthtransistor TR5 may have a threshold voltage greater than that of thefourth transistor TR4, and the sixth transistor TR6 may have a thresholdvoltage greater than that of the fifth transistor TR5.

The fourth work function pattern WF4 of the fourth transistor TR4 mayinclude a first work function metal layer W1 and a third work functionmetal layer W3 stacked, e.g. sequentially stacked, on the secondsemiconductor pattern NS2. The fifth work function pattern WF5 of thefifth transistor TR5 may include a first work function metal layer W1and a third work function metal layer W3 sequentially stacked on thesecond semiconductor pattern NS2. For example, the material included inthe fourth work function pattern WF4 may be the same, or substantiallythe same, as that included in the fifth work function pattern WF5. Thethird work function metal layer W3 may be or include a work functionmetal layer used in an NMOSFET, and may be or include a metal layerhaving a relatively low work function. For example, the third workfunction metal layer W3 may be or include a TiAlC layer.

A work function control liner CL may be between the fourth work functionpattern WF4 and the second semiconductor patterns NS2. The work functioncontrol liner CL of the fourth transistor TR4 may be the same, orsubstantially the same, as the work function control liner CL of thesecond transistor TR discussed above. The work function control liner CLof the fourth transistor TR may generate a dipole, and in contrast tothe PMOSFET, the fourth transistor TR4 as the NMOSFET may decrease inthreshold voltage.

In conclusion, even though all of the fourth and fifth work functionpatterns WF4 and WF5 have only the same first and third work functionmetal layers W1 and W3, the work function control liner CL may cause thefifth transistor TR5 to have a threshold voltage greater than that ofthe fourth transistor TR4.

The sixth work function pattern WF6 of the sixth transistor TR6 mayinclude a first work function metal layer W1, a second work functionmetal layer W2, other first work function metal layer W1, and a thirdwork function metal layer W3 sequentially stacked on the secondsemiconductor pattern NS2. The second work function metal layer W2 ofthe sixth work function pattern WF6 may have a thickness less than thatof the second work function metal layer W2 of the third work functionpattern WF3. A combination of work function metal layers W1, W2, W1, andW3 may be employed to cause the sixth work function pattern WF6 to havea work function different from those of the fourth and fifth workfunction patterns WF4 and WF5. As a result, the sixth transistor TR6 mayhave a threshold voltage greater than that of the fifth transistor TR5.

Optionally or additionally, a work function control liner CL may bebetween the sixth work function pattern WF6 and the second semiconductorpatterns NS2. The work function control liner CL may prevent the sixthtransistor TR6 from excessively increasing its threshold voltage.

A first interlayer dielectric layer 110 may be provided on an entiresurface of the substrate 100. The first interlayer dielectric layer 110may cover, e.g. directly cover, the device isolation layer ST, the firstto sixth gate electrodes GE1 to GE6, and the first and secondsource/drain patterns SD1 and SD2. The first interlayer dielectric layer110 may have a top surface coplanar, or substantially coplanar, withthose of the gate capping layers GP. For example, the first interlayerdielectric layer 110 may include a silicon oxide layer or a siliconoxynitride layer.

Although not shown, contacts may be provided to penetrate the firstinterlayer dielectric layer 110 to come into contact with the first andsecond source/drain patterns SD1 and SD2. The contacts may include ametallic material such as T1, W, and Ta.

FIGS. 3, 5, 7, and 9 illustrate plan views showing a method ofmanufacturing a semiconductor device according to some exampleembodiments of inventive concepts. FIGS. 4A, 6A, 8A, and 10A illustratecross-sectional views taken along line A-A′ of FIGS. 3, 5, 7, and 9,respectively. FIGS. 4B, 6B, 8B, and 10B illustrate cross-sectional viewstaken along line B-B′ of FIGS. 3, 5, 7, and 9, respectively. FIG. 10Cillustrates a cross-sectional view taken along line C-C′ of FIG. 9. FIG.10D illustrates a cross-sectional view taken along line D-D′ of FIG. 9.FIGS. 11 to 14 illustrate cross-sectional views showing a method offorming first to third gate electrodes according to some exampleembodiments of inventive concepts.

Referring to FIGS. 3, 4A, and 4B, sacrificial layers 120 andsemiconductor layers 130 may be alternately and repeatedly stacked on anentire surface of a substrate 100. The semiconductor layers 130 may berepeatedly stacked three times, but inventive concepts are not limitedthereto. In some embodiments, the sacrificial layers 120 may include amaterial having an etch selectivity to the semiconductor layers 130. Forexample, the semiconductor layers 130 may include a material that is notetched in a process where the sacrificial layers 120 are etched.Specifically, in the process where the sacrificial layers 120 areetched, an etch rate ratio of the sacrificial layers 120 to thesemiconductor layers 130 may fall within a range from about 10:1 toabout 200:1. For example, the sacrificial layers 120 may include SiGe orGe, and the semiconductor layers 130 may include Si.

The sacrificial layers 120 and the semiconductor layers 130 may beformed by an epitaxial growth process in which the substrate 100 is usedas a seed layer. The sacrificial layers 120 and the semiconductor layers130 may be successively formed in the same chamber, for example, thesame CVD chamber. The sacrificial layers 120 and the semiconductorlayers 130 may be conformally formed on the entire surface of thesubstrate 100.

The sacrificial layers 120, the semiconductor layers 130, and thesubstrate 100 may be patterned to form a first preliminary activepattern PAP1 and a second preliminary active pattern PAP2. Thepatterning process may also etch an upper portion of the substrate 100to form first and second upper patterns UP1 and UP2. The first andsecond preliminary active patterns PAP1 and PAP2 may be respectively onthe first and second upper patterns UP1 and UP2. The first and secondpreliminary active patterns PAP1 and PAP2 may have a linear or bar shapeextending in a second direction D2.

When the upper portion of the substrate 100 is etched by the patterningprocess, trenches may be formed on opposite sides of each of the firstand second upper patterns UP1 and UP2. A device isolation layer ST maybe formed to fill the trenches. The formation of the device isolationlayer ST may include forming an insulation layer on the entire surfaceof the substrate 100 and recessing the insulation layer until the firstand second preliminary active patterns PAP1 and PAP2 are completelyexposed. Accordingly, the device isolation layer ST may have a topsurface lower than those of the first and second upper patterns UP1 andUP2.

Referring to FIGS. 5, 6A, and 6B, sacrificial gate patterns 140 may beformed to run across the first and second preliminary active patternsPAP1 and PAP2. The sacrificial gate patterns 140 may be formed to have alinear or bar shape extending in a first direction D1. Gate maskpatterns MP may correspondingly be formed on the sacrificial gatepatterns 140. The formation of the sacrificial gate patterns 140 and thegate mask patterns MP may include sequentially forming on the substrate100 a sacrificial gate layer and a gate mask layer, and sequentiallypatterning the gate mask layer and the sacrificial gate layer. Thesacrificial gate layer may include polysilicon. The gate mask layer mayinclude a silicon nitride layer and/or a silicon oxynitride layer.

A pair of gate spacers GS may be formed on opposite sidewalls of each ofthe sacrificial gate patterns 140. For example, the gate spacers GS mayinclude one or more of SiCN, SiCON, and SiN. The formation of the gatespacers GS may include forming a spacer layer by a deposition processsuch as CVD or atomic layer deposition (ALD) and performing ananisotropic etching process on the spacer layer.

Referring to FIGS. 7, 8A, and 8B, the first and second preliminaryactive patterns PAP1 and PAP2 may be patterned to respectively formfirst and second channel patterns CH1 and CH2. The first and secondpreliminary active patterns PAP1 and PAP2 may be patterned using thegate mask patterns MP and the gate spacers GS as an etching mask. Thefirst and second upper patterns UP1 and UP2 may therefore be partiallyexposed through the gate mask patterns MP and the gate spacers GS.

For example, the sacrificial layers 120 of the first and secondpreliminary active patterns PAP1 and PAP2 may be patterned to formsacrificial patterns 125. The semiconductor layers 130 of the first andsecond preliminary active patterns PAP1 and PAP2 may be patterned toform first and second semiconductor patterns NS1 and NS2. The firstsemiconductor patterns NS1 may be included in the first channel patternCH1, and the second semiconductor patterns NS2 may be included in thesecond channel pattern CH2.

After the patterning process, exposed portions of the sacrificialpatterns 125 may be horizontally removed to form depression regions DR.The formation of the depression regions DR may include performing anetching process using an etch source that exhibits an etch selectivityto the sacrificial patterns 125. The etching process may include a wetetching process. For example, when the first and second semiconductorpatterns NS1 and NS2 include Si, and when the sacrificial patterns 125include SiGe, the formation of the depression regions DR may includeperforming an etching process with an etchant including peracetic acid.

Barrier insulation patterns BP may be formed to fill the depressionregions DR. The barrier insulation patterns BP may be vertically spacedapart from each other across the first and second semiconductor patternsNS1 and NS2. For example, a barrier insulation layer may be conformallyformed on the entire surface of the substrate 100. The barrierinsulation layer may fill the depression regions DR. After that, thebarrier insulation layer may be etched until the barrier insulationpatterns BP remain locally in the depression regions DR.

First source/drain patterns SD1 may be formed on opposite sides of eachof the first channel patterns CH1. Second source/drain patterns SD2 maybe formed on opposite sides of each of the second channel patterns CH2.

For example, a selective epitaxial process may be performed using thefirst semiconductor patterns NS1 and the first upper pattern UP1 as aseed layer, thereby forming the first source/drain patterns SD1. Thefirst channel patterns CH1 and the first source/drain patterns SD1 maybe connected to each other to be included in a first active pattern AP1extending in the second direction D2. The first source/drain patternsSD1 may be formed of a material that provides compressive strain to thefirst channel patterns CH1. For example, the first source/drain patternsSD1 may include SiGe whose lattice constant is greater than that of Si.Accordingly a mobility of carriers, e.g. hole mobility, may increase ina channel during operation of the transistor. Simultaneously during orafter the selective epitaxial process, the first source/drain patternsSD1 may be doped with P-type impurities, for example, boron (B).

A selective epitaxial process may be performed using the secondsemiconductor patterns NS2 and the second upper pattern UP2 as a seedlayer, thereby forming the second source/drain patterns SD2. The secondchannel patterns CH2 and the second source/drain patterns SD2 may beconnected to each other to be included in a second active pattern AP2extending in the second direction D2. For example, the secondsource/drain patterns SD2 may be formed of Si. Simultaneously during orafter the selective epitaxial process, the second source/drain patternsSD2 may be doped with N-type impurities, for example, phosphorus (P)and/or arsenic (As).

Referring to FIGS. 9 and 10A to 10D, a first interlayer dielectric layer110 may be formed on the entire surface of the substrate 100.Thereafter, a planarization process may be performed on the firstinterlayer dielectric layer 110 until top surfaces of the sacrificialgate patterns 140 are exposed. The planarization process may include anetch-back process and/or a chemical mechanical polishing (CMP) process.When the first interlayer dielectric layer 110 is planarized, the gatemask patterns MP may also be removed. For example, the first interlayerdielectric layer 110 may be formed of a silicon oxide layer or a siliconoxynitride layer.

The planarization process may selectively remove the exposed sacrificialgate patterns 140. As the sacrificial gate patterns 140 are removed,first to sixth trenches TC1 to TC6 may be respectively formed on firstto sixth regions RG1 to RG6 of the substrate 100. The first to sixthtrenches TC1 to TC6 may expose the first and second channel patterns CH1and CH2. The first to sixth trenches TC1 to TC6 may also expose thesacrificial patterns 125.

The exposed sacrificial patterns 125 may be selectively removed, forexample, with a wet etching process. For example, when the sacrificialpatterns 125 include SiGe, and when the first and second semiconductorpatterns NS1 and NS2 include Si, the selective etching process may beperformed using an etchant including peracetic acid. The etchant mayfurther include a hydrofluoric acid (HF) solution and a deionized water.The first and second source/drain patterns SD1 and SD2 may be coveredwith the barrier insulation patterns BP and the first interlayerdielectric layer 110, and may thereby be protected from the etchingprocess.

The sacrificial patterns 125 may be removed to form first to sixthspaces SP1 to SP6 on the first to sixth regions RG1 to RG6. The first tosixth spaces SP1 to SP6 may be respectively spatially connected to thefirst to sixth trenches TC1 to TC6 to expose the first and secondsemiconductor patterns NS1 and NS2.

Referring back to FIGS. 1 and 2A to 2D, first to sixth gate electrodesGE1 to GE6 may be respectively formed in the first to sixth trenches TC1to TC6. The formation of the first to sixth gate electrodes GE1 to GE6will be discussed below with reference to FIGS. 11 to 14. Gate cappinglayers CP may be formed on the first to sixth gate electrodes GE1 toGE6. For example, the gate capping layers CP may include one or more ofSiON, SiCN, SiCON, and SiN. Although not shown, contacts may be formedto penetrate the first interlayer dielectric layer 110 to come intocontact with the first and second source/drain patterns SD1 and SD2.

The formation of the first to sixth gate electrodes GE1 to GE6 in thefirst to sixth trenches TC1 to TC6 will be discussed below withreference to FIGS. 11 to 14. The formation of the first to third gateelectrodes GE1 to GE3 will be representatively described below.

Referring to FIG. 11, an oxidation process using plasma may be performedon the first semiconductor patterns NS1 exposed to the first to thirdtrenches TC1 to TC3, and therefore interface layers IL may be grown fromthe exposed first semiconductor patterns NS1. The interface layers ILmay surround, e.g. directly surround, surfaces of the exposed firstsemiconductor patterns NS1.

The formation of the interface layer IL may include a thermal oxidationprocess and/or a chemical oxidation process. The oxidation process mayuse one or more of oxygen plasma, ozone plasma, and vapor plasma. Theinterface layers IL may include, for example, a silicon oxide layer.

Gate dielectric layers GI may be conformally formed on the interfacelayers IL. The gate dielectric layers GI may partially fill the first tothird spaces SP1 to SP3 of the first to third trenches TC1 to TC3. Thegate dielectric layers GI may directly cover the barrier insulationpatterns BP and the interface layers IL. The gate dielectric layers GImay be formed using a high-k dielectric material whose dielectricconstant is greater than that of a silicon oxide layer.

Referring to FIG. 12, a first mask pattern MA1 may be formed on thefirst and second regions RG1 and RG2. The first mask pattern MA1 mayselectively expose the third region RG3. The first mask pattern MA1 mayfill, e.g. completely fill, the first and second trenches TC1 and TC2.The first mask pattern MA1 may not fill the third trench TC3.

A third work function pattern WF3 may be formed in the third trench TC3selectively exposed through the first mask pattern MA1. The third workfunction pattern WF3 may be formed to completely fill the third spaceSP3 of the third trench TC3.

The formation of the third work function pattern WF3 may includeconformally forming a first work function metal layer W1 in the thirdtrench TC3, conformally forming a second work function metal layer W2 inthe third trench TC3, conformally forming other first work functionmetal layer W1 in the third trench TC3, and recessing upper portions ofthe first and second work function metal layers W1 and W2. The first andsecond work function metal layers W1 and W2 may be formed by adeposition process such as ALD. The first work function metal layer W1may be or include a metal nitride layer having a relatively higher workfunction, and the second work function metal layer W2 may be or includea metal nitride layer having a relatively lower work function that thatof the first work function metal layer W1.

Referring to FIG. 13, the first mask pattern MA1 may be removed. Asecond mask pattern MA2 may be formed on the first and third regions RG1and RG3. The second mask pattern MA2 may selectively expose the secondregion RG2. The second mask pattern MA2 may fill, e.g. completely fill,the first and third trenches TC1 and TC3. The second mask pattern MA2may not fill the second trench TC2.

A work function control liner CL and a second work function pattern WF2may be sequentially formed in the second trench TC2 selectively exposedthrough the second mask pattern MA2. The second work function patternWF2 may be formed to fill, e.g. completely fill, the second space SP2 ofthe second trench TC2.

The work function control liner CL may be conformally formed by adeposition process such as ALD. The work function control liner CL maybe formed using a high-k dielectric material whose dielectric constantis greater than that of a silicon oxide layer. The formation of thesecond work function pattern WF2 may include conformally forming a firstwork function metal layer W1 in the second trench TC2 and recessing anupper portion of the first work function metal layer W1.

Referring to FIG. 14, the second mask pattern MA2 may be removed. Athird mask pattern MA3 may be formed on the second and third regions RG2and RG3. The third mask pattern MA3 may selectively expose the firstregion RG1. The third mask pattern MA3 may fill, e.g. completely fill,the second and third trenches TC2 and TC3. The third mask pattern MA3may not fill the first trench TC1.

A first work function pattern WF1 may be formed in the first trench TC1selectively exposed through the third mask pattern MA3. The first workfunction pattern WF1 may be formed to completely fill the first spaceSP1 of the first trench TC1. The formation of the first work functionpattern WF1 may include conformally forming a first work function metallayer W1 in the first trench TC1 and recessing an upper portion of thefirst work function metal layer W1.

Referring back to FIG. 2A, the third mask pattern MA3 may be removed.First to third electrode patterns EL1 to EL3 may be respectively formedin the first to third trenches TC1 to TC3. The first to third electrodepatterns EL1 to EL3 may be respectively formed on the first to thirdwork function patterns WF1 to WF3. The first to third electrode patternsEL1 to EL3 may be formed using a low resistance, or low resistivity,metal.

Fourth to sixth gate electrodes GE4 to GE6 may be formed using formationmethods similar to those of the first to third gate electrodes GE1 toGE3 discussed above with reference to FIGS. 11 to 14. In someembodiments, gate-all-around type transistors having different thresholdvoltages from each other may be selectively formed on the first to sixthregions RG1 to RG6.

FIG. 15 illustrates an enlarged cross-sectional view of section M ofFIG. 2B, partially showing a sixth transistor of a semiconductor deviceaccording to some example embodiments of inventive concepts. In theembodiment that follows, a detailed description of technical featuresrepetitive to those formerly discussed with reference to FIGS. 1 and 2Ato 2D will be omitted and differences will be discussed in detail.

Referring to FIG. 15, unlike that shown in FIG. 2B, the sixth gateelectrode GE6 may include layers whose thicknesses are different fromeach other. The first work function metal layer W1 of the sixth workfunction pattern WF6 may have a thickness greater than that of thesecond work function metal layer W2 of the sixth work function patternWF6. For example, in the sixth space SP6, at least one of the first workfunction metal layers W1 may have a first thickness T1, and the secondwork function metal layer W2 may have a second thickness T2. The firstthickness T1 may be greater than the second thickness T2.

The third work function metal layer W3 of the sixth work functionpattern WF6 may have a thickness greater than that of each of the firstand second work function metal layers W1 and W2 of the sixth workfunction pattern WF6. For example, in the sixth space SP6, the thirdwork function metal layer W3 may have a third thickness T3. The thirdthickness T3 may be greater than the first thickness T1.

A semiconductor device according to some example embodiments ofinventive concepts may be configured such that the gate-all-around typetransistors are achieved to have various threshold voltages caused by acombination of work function metal layers.

Although some example embodiments of inventive concepts have beendiscussed with reference to accompanying figures, it will be understoodthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present inventive concept. Ittherefore will be understood that the embodiments described above arejust illustrative but not limitative in all aspects.

1. A semiconductor device, comprising: a first transistor on asubstrate; and a second transistor on the substrate, wherein each of thefirst and second transistors includes, a plurality of semiconductorpatterns vertically stacked on the substrate and vertically spaced apartfrom each other, and a gate dielectric pattern and a work functionpattern filling a space between the semiconductor patterns, wherein thework function pattern of the first transistor includes a first workfunction metal layer, the work function pattern of the second transistorincludes the first work function metal layer and a second work functionmetal layer, the first work function metal layer of each of the firstand second transistors has a work function greater than that of thesecond work function metal layer, and the first transistor has athreshold voltage less than that of the second transistor.
 2. The deviceof claim 1, wherein the work function pattern of each of the first andsecond transistors completely fills the space between the semiconductorpatterns.
 3. The device of claim 1, wherein each of the first and secondtransistors further comprises an electrode pattern on the work functionpattern, and the electrode pattern has resistance less than that of thework function pattern and does not fill the space.
 4. The device ofclaim 1, wherein the first work function metal layer of each of thefirst and second transistors comprises a metal nitride layer, and thesecond work function metal layer comprises a metal nitride layer dopedwith an element from the group including silicon and aluminum.
 5. Thedevice of claim 4, wherein a silicon or aluminum doping concentration ofthe second work function metal layer is in a range from about 10 at % toabout 30 at %.
 6. The device of claim 1, wherein the first transistorfurther includes a work function control liner between the work functionpattern and the semiconductor patterns, and the work function controlliner is configured to generate a dipole that changes a thresholdvoltage of the first transistor.
 7. The device of claim 1, furthercomprising: a third transistor on the substrate; and a fourth transistoron the substrate, wherein each of the third and fourth transistorsincludes a plurality of semiconductor patterns vertically stacked on thesubstrate and vertically spaced apart from each other, and a gatedielectric pattern and a work function pattern that fill a space betweenthe semiconductor patterns, wherein the work function pattern of thethird transistor includes the first work function metal layer and athird work function metal layer, the work function pattern of the fourthtransistor includes the first work function metal layer, the second workfunction metal layer, and the third work function metal layer, the thirdwork function metal layer of each of the third and fourth transistorshas a work function less than that of the second work function metallayer of the fourth transistor, the first and second transistors arePMOSFETs, and the third and fourth transistors are NMOSFETs.
 8. Thedevice of claim 7, wherein the second work function metal layer of thesecond transistor has a thickness greater than that of the second workfunction metal layer of the fourth transistor.
 9. The device of claim 1,wherein the work function pattern of each of the first and secondtransistors surrounds a top surface, a bottom surface, and sidewalls ofthe semiconductor patterns.
 10. The device of claim 1, wherein each ofthe first and second transistors further includes a pair of source/drainpatterns, and the plurality of semiconductor patterns vertically stackedare between the pair of source/drain patterns.
 11. A semiconductordevice, comprising: a first transistor on a substrate; and a secondtransistor on the substrate, wherein each of the first and secondtransistors includes, a plurality of semiconductor patterns verticallystacked on the substrate and vertically spaced apart from each other,and a gate dielectric pattern and a work function pattern that fill aspace between the semiconductor patterns, wherein the space of the firsttransistor has the same size as that of the space of the secondtransistor, the work function pattern of the first transistor comprisesa first work function metal layer, the work function pattern of thesecond transistor comprises the first work function metal layer and asecond work function metal layer, and the first transistor has athreshold voltage different from that of the second transistor.
 12. Thedevice of claim 11, wherein the work function pattern in the space ofthe first transistor has a thickness the same as that of the workfunction pattern in the space of the second transistor.
 13. The deviceof claim 11, wherein the first work function metal layer of each of thefirst and second transistors comprises a metal nitride layer, and thesecond work function metal layer comprises a metal nitride layer dopedwith an element from the group including silicon and aluminum.
 14. Thedevice of claim 11, wherein the first and second transistors arePMOSFETs, the first work function metal layer of each of the first andsecond transistors has a work function greater than that of the secondwork function metal layer, and the second work function metal layer ofthe second transistor has a thickness greater than that of the firstwork function metal layer of the second transistor.
 15. The device ofclaim 11, wherein the first and second transistors are PMOSFETs, thefirst work function metal layer of each of the first and secondtransistors has a work function greater than that of the second workfunction metal layer, and the second work function metal layer of thesecond transistor has a thickness less than that of the first workfunction metal layer of the second transistor.
 16. A method ofmanufacturing a semiconductor device, the method comprising: formingsacrificial layers and semiconductor layers alternately and repeatedlystacked on a substrate; forming sacrificial gate patterns crossing overthe sacrificial layers and the semiconductor layers and extending in onedirection; removing the sacrificial gate patterns to form a first trenchand a second trench that expose the semiconductor layers and thesacrificial layers; selectively removing the sacrificial layers exposedto the first and second trenches; forming a first work function patternthat fills a first space between the semiconductor layers in the firsttrench; and forming a second work function pattern that fills a secondspace between the semiconductor layers in the second trench, wherein thefirst work function pattern comprises a first work function metal layer,the second work function pattern comprises a first work function metallayer and a second work function metal layer, the first space and thesecond space have the same size as each other, and the first workfunction pattern and the second work function pattern have differentwork functions from each other.
 17. The method of claim 16, beforeforming the first work function pattern, further comprising forming awork function control liner that partially fills the first space,wherein the work function control liner is configured to generate adipole that changes the work function of the first work functionpattern.
 18. The method of claim 16, before forming the first and secondwork function patterns, further comprising forming a gate dielectriclayer that partially fills the first and second spaces.
 19. The methodof claim 16, wherein the first space includes a region where thesacrificial layer exposed to the first trench is removed, and the secondspace includes a region where the sacrificial layer exposed to thesecond trench is removed.
 20. The method of claim 16, furthercomprising: forming a first mask pattern that covers the second trenchand exposes the first trench; and forming a second mask pattern thatcovers the first trench and exposes the second trench, wherein the firstand second work function patterns are formed using the first and secondmask patterns, respectively.